Well, this could change things (neutrinos)

[eSOANEM]

PS eSOANEM, is it not because it actually breaks all the equations. It does not force us to change the rules, it removes all possible rules or systems of expression (maths, logic etc) completely.

No, the equations work fine (which is why relativity is still consistent when you allow tachyons), it just makes it harder to make predictions because in some cases you may need to know the future state of something in order to get the right result (note, the something would not necessarily be the thing being measured so this doesn't have to lead to circular logic).

[Wombat2k]

String theory is very cool. That`s one of my problems with it. It`s a very seductive hypothosis. I want it to be true.
Things that I find cool have to be held at a higher standard of evidence than things that are boring.
In the past I`ve made hypotheses that fit all the data and just run with them because of lack of time. After being wrong over and over I learned to test more and more. Peers and QA have caught all (hopefully) mistakes. So the experiment needs to be repeated. The results verified.
But still gonna be reading papers on string theory neutrinos. (it`s stll cool..just probably not true)

[BlackSails]

What about if the measured speed of light is off from the true speed of light? I could imagine photons interact with the background in someway such that the speed of light in vacuum is not the true speed of light, might like how the speed of light in glass is reduced.

Time dilation has been accurately measured, as have other relativistic effects in many different situations. These all depend on c, but not on directly measuring the speed of photons in any medium.

What if time dilation and all that depend on the "effective" c, which is screened by whatever magical vacuum effects there are that dont affect neutrinos?

I think that's was jaap's point: we've measured it accurately enough to know that that's not true.

What I mean is take c in all the special relativity equations, and replace it by c'. c' is the effective speed of light.

This is sort of how the electron mass in any equation is the effective electron mass, after renormalization.

[Technical Ben]

PS eSOANEM, is it not because it actually breaks all the equations. It does not force us to change the rules, it removes all possible rules or systems of expression (maths, logic etc) completely.

No, the equations work fine (which is why relativity is still consistent when you allow tachyons), it just makes it harder to make predictions because in some cases you may need to know the future state of something in order to get the right result (note, the something would not necessarily be the thing being measured so this doesn't have to lead to circular logic).

Ok. I seem to have missed something though. With the infinate energy requirement for accelerating particles. It's the discrepancy in the neutrinos speed that is the problem so far. If we had always detected FTL, then perhaps it would have just been "cool, tachyons" and had an answer. With the change in speed does it break things badly?

[PM 2Ring]

What I mean is take c in all the special relativity equations, and replace it by c'. c' is the effective speed of light.

This is sort of how the electron mass in any equation is the effective electron mass, after renormalization.

That was one of the options I considered when this neutrino news first broke. Unfortunately, it doesn't work: we've measured c by measuring the actual speed of light, and we've also checked the value of c as used in the Lorentz transforms (eg time dilation, length contraction, and mass-energy equivalence & 4-momentum conservation), eg in particle accelerator experiments, and the values agree. We know the speed of light to quite a few significant figures, but I'm not sure how many sig figs we have for the Lorentz c constant, but I expect it to be fairly good, since we can accelerate particles to rather high gamma values.

[Arkham]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

[gmalivuk]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

GPS just tells you your position, actually. Calculating the distance is then up to you.

[Arkham]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

GPS just tells you your position, actually. Calculating the distance is then up to you.

Yes, what i mean to say is, did they factor the curvature of the earth when they did their measurements in between point A and point B.

[Game_boy]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

GPS just tells you your position, actually. Calculating the distance is then up to you.

Yes, what i mean to say is, did they factor the curvature of the earth when they did their measurements in between point A and point B.

Wow, I think you've just outsmarted hundreds of scientists who've been thinking about this problem for over three years now.

[Arkham]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

GPS just tells you your position, actually. Calculating the distance is then up to you.

Yes, what i mean to say is, did they factor the curvature of the earth when they did their measurements in between point A and point B.

Wow, I think you've just outsmarted hundreds of scientists who've been thinking about this problem for over three years now.

Told you it was a dumb question, but even those have to be asked.

[Malconstant]

Wow, I think you've just outsmarted hundreds of scientists who've been thinking about this problem for over three years now.

This should pretty much be the banner post which anyone else in this thread should have to consider. This goes both for imagined possible systematic experimental errors, and for the presumption that theorists are unwilling to consider the experiment might be valid, pathetically clinging onto now-useless physics of a past era. It's really hard to tell the difference between trolling and staggering ignorance with respect to these.

This doesn't apply to those who have read this whole thread and have an honest question for clarification. There ain't nothin wrong with sharing knowledge, so long as you give the scientific community their due.

[Arkham]

Wow, I think you've just outsmarted hundreds of scientists who've been thinking about this problem for over three years now.

This should pretty much be the banner post which anyone else in this thread should have to consider. This goes both for imagined possible systematic experimental errors, and for the presumption that theorists are unwilling to consider the experiment might be valid, pathetically clinging onto now-useless physics of a past era. It's really hard to tell the difference between trolling and staggering ignorance with respect to these.

This doesn't apply to those who have read this whole thread and have an honest question for clarification. There ain't nothin wrong with sharing knowledge, so long as you give the scientific community their due.

So DID they consider this? I have not read the research paper so i dont know. And even my initial post said 'i'm almost sure they thought of this but...."

[Malconstant]

So DID they consider this? I have not read the research paper so i dont know. And even my initial post said 'i'm almost sure they thought of this but...."

Yes, they did think about this. Your noted skepticism of it being a novel consideration was well-placed.

[Carnildo]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

Far less. A back-of-the-envelope calculation is that the straight-line distance from CERN to OPERA is about 500 meters less than the curved distance, which would have the neutrinos arrive about 1600 nanoseconds early rather than the observed 60 nanoseconds.

[eSOANEM]

PS eSOANEM, is it not because it actually breaks all the equations. It does not force us to change the rules, it removes all possible rules or systems of expression (maths, logic etc) completely.

No, the equations work fine (which is why relativity is still consistent when you allow tachyons), it just makes it harder to make predictions because in some cases you may need to know the future state of something in order to get the right result (note, the something would not necessarily be the thing being measured so this doesn't have to lead to circular logic).

Ok. I seem to have missed something though. With the infinate energy requirement for accelerating particles. It's the discrepancy in the neutrinos speed that is the problem so far. If we had always detected FTL, then perhaps it would have just been "cool, tachyons" and had an answer. With the change in speed does it break things badly?

The infinite energy is only a problem if the particles were accelerated to superluminal velocities. If all neutrinos are always superluminal or if there was some interaction whereby subluminal neutrinos decayed into superluminal neutrinos, no such acceleration would have taken place (as there would simply be new particles travelling superluminally) and so, other than the time travel issue, nothing borks.

[mfb]

Dumb question, but i'm assuming they factored in the fact that GPS reports the distance over a curved surface, while the nutrenos would be going a straight line through the earth, and thus would have a slightly less distance to travel, right?

They used a three-dimensional coordinate system, so they did not only account for that, but also for the fact that the earth is not a sphere and that sender&receiver are at different height. All three effects are larger than 20m.

[Technical Ben]

Spoiler:

PS eSOANEM, is it not because it actually breaks all the equations. It does not force us to change the rules, it removes all possible rules or systems of expression (maths, logic etc) completely.

No, the equations work fine (which is why relativity is still consistent when you allow tachyons), it just makes it harder to make predictions because in some cases you may need to know the future state of something in order to get the right result (note, the something would not necessarily be the thing being measured so this doesn't have to lead to circular logic).

Ok. I seem to have missed something though. With the infinate energy requirement for accelerating particles. It's the discrepancy in the neutrinos speed that is the problem so far. If we had always detected FTL, then perhaps it would have just been "cool, tachyons" and had an answer. With the change in speed does it break things badly?

The infinite energy is only a problem if the particles were accelerated to superluminal velocities. If all neutrinos are always superluminal or if there was some interaction whereby subluminal neutrinos decayed into superluminal neutrinos, no such acceleration would have taken place

(as there would simply be new particles travelling superluminally) and so, other than the time travel issue, nothing borks.

Oooh. Yep, that bit I did not guess. Clever Girl particle! (In fact, it would make that scene ever better. How about a time travelling Raptor!!!)

[Arkham]

http://xxx.lanl.gov/PS_cache/arxiv/pdf/ ... 6160v2.pdf

Basically they are claiming that

The CERN-OPERA experiment claims to have measured a one-way speed of neutrinos that is apparently faster than the speed of light c. One-way speed measurements such as these inevitably require a convention for the synchronisation of clocks in non-inertial frames since the Earth is rotating. We argue that the effect of the synchronisation convention is not properly taken into account in the OPERA analysis and may well invalidate their interpretation of superluminal neutrino velocity.

Less technical article:
http://www.nature.com/news/2011/111005/ ... 1.575.html

[gorcee]

Thanks, Arkham. That's a fascinating paper.

[Aiwendil]

Another good paper: http://arxiv.org/PS_cache/arxiv/pdf/110 ... 6562v1.pdf

Essentially, they show that superluminal neutrinos would pair produce at a high enough rate that they would rapidly lose energy. This would lead to a significant distortion of the energy spectrum of the observed neutrinos - a distortion that OPERA does not see. So any interpretation of the OPERA result that claims the neutrinos are indeed superluminal would have to explain why they are not pair producing - which is pretty hard to do.

[Arkham]

Another good paper: http://arxiv.org/PS_cache/arxiv/pdf/110 ... 6562v1.pdf

Essentially, they show that superluminal neutrinos would pair produce at a high enough rate that they would rapidly lose energy. This would lead to a significant distortion of the energy spectrum of the observed neutrinos - a distortion that OPERA does not see. So any interpretation of the OPERA result that claims the neutrinos are indeed superluminal would have to explain why they are not pair producing - which is pretty hard to do.

From a layman's standpoint however, all I'm getting out of this is someone claiming it could not possibly be true, but not explaining why they are getting the result they are. Not sure how useful that actually is.

[Aiwendil]

From a layman's standpoint however, all I'm getting out of this is someone claiming it could not possibly be true, but not explaining why they are getting the result they are. Not sure how useful that actually is.

Well, the paper isn't trying to provide an explanation for the OPERA result, but it is providing a pretty stringent condition on what sorts of explanations are possible. Namely, that explanations involving superluminal neutrinos are out, unless they also provide some novel mechanism to avoid pair production. Since no one has come up with such a mechanism, it's a pretty good bet that the explanation is not superluminal neutrinos.

[gorcee]

Another good paper: http://arxiv.org/PS_cache/arxiv/pdf/110 ... 6562v1.pdf

Essentially, they show that superluminal neutrinos would pair produce at a high enough rate that they would rapidly lose energy. This would lead to a significant distortion of the energy spectrum of the observed neutrinos - a distortion that OPERA does not see. So any interpretation of the OPERA result that claims the neutrinos are indeed superluminal would have to explain why they are not pair producing - which is pretty hard to do.

From a layman's standpoint however, all I'm getting out of this is someone claiming it could not possibly be true, but not explaining why they are getting the result they are. Not sure how useful that actually is.

Sure they do.

They set up the moving clock problem, show how, with a couple of reasonable numbers plucked out of the air (since the real numbers aren't available), that the possible error is on the order of the error that the OPERA team witnessed. So it's a perfectly good explanation of why the OPERA team may be getting the result they are, but the validation is impossible until the OPERA team publishes details of their moving clock calibration.

[Technical Ben]

So the moving atomic clock took a route over a mountain, said mountain/altitude change was not accounted for and relativity/gravity is too blame for the subsequent 60-70ns? Oh, rather an easy one to find out then?

[doogly]

Moving clock does not refer to putting the clock in a truck and moving it. It is special relativity.

[gorcee]

So the moving atomic clock took a route over a mountain, said mountain/altitude change was not accounted for and relativity/gravity is too blame for the subsequent 60-70ns? Oh, rather an east one to find out then?

Basically, one-way measurements at lightspeed are tricky, because you need a timer at the sender and the receiver, and these timers need to be in sync to a very high degree of accuracy.

How do you get that?

Well, say you had a super-accurate clock that you can carry around. You start at the sending end, and use this super accurate clock to calibrate your sending timer. Then, you lug the clock to the receiving end, and you calibrate the receiving timer.

Now, both the sending and receiving timers should be sync'd up, because you sync'd both of them off the same super-accurate clock, right?

Right. Except not.

That super accurate clock that you lug around has to go from one place to another, which means that it is going to undergo time dilation effects from various sources of special relativity (the paper lists three). So you need to know the magnitude of these effects that can accumulate in the time between calibrating the sender and the receiver.

So there's good news about this. This means that they can repeat the synchronization and calibration of the timers at CERN and OPERA and see if they observe the same effect, or if that TOF delta is different. They can also do the calibration in reverse order, to see if we get subluminal neutrinos instead of superluminal ones. This would be easier and faster than waiting on a different detector to attempt the same results.

[Technical Ben]

Moving clock does not refer to putting the clock in a truck and moving it. It is special relativity.

Sorry, reading fail of the report. I thought it said they did, when it said they reported it might have been done.

The report says

Dario Autiero of the Institute of Nuclear Physics in Lyons (IPNL), France, and physics coordinator for OPERA, counters that Contaldi's challenge is a result of a misunderstanding of how the clocks were synchronized.

and

Contaldi admits that his original analysis posted at arXiv wrongly assumed that OPERA's timings relied on a clock being moved from one end of the beam to the other. But even synchronizing the clocks using GPS does not remove the difference in the time dilation effect, which Contaldi says could amount to tens of nanoseconds.

So still unsure how they did the clocks anyhow.

[ibgdude]

This article:
EDIT:
Correct article:
http://arxiv.org/PS_cache/arxiv/pdf/1110/1110.0239v1.pdf

Spoiler:

Incorrect article:

Less technical article:
http://www.nature.com/news/2011/111005/ ... 1.575.html

seems to be saying that a change in the cross section of the neutrinos, a change in their probability of detection, I guess, might give the appearance of a shift in time forwards. However, I can't quite figure out what the paper means by this. Can anyone explain it more simply? Quote from the article: "The apparent shift in TOF is thus of the order of the relative variation of the cross section times the rising time of the bunch. Note that an apparent advance of the rising edge can be obtained with negative values of [epsilon], that is average cross section decreasing with time."

[Minerva]

Contaldi admits that his original analysis posted at arXiv wrongly assumed that OPERA's timings relied on a clock being moved from one end of the beam to the other. But even synchronizing the clocks using GPS does not remove the difference in the time dilation effect, which Contaldi says could amount to tens of nanoseconds.

One part of their process of timekeeping, checking and calibration did involve physically moving a small portable caesium clock between both the CERN and Gran Sasso sites.

[Afif_D]

If they mean to say that Sir Alber Einstein is wrong then how did his formulas and theorems work out well this long?

[Shivahn]

Newton's forumlae worked for longer than Einstein's. How did those work out for so long?

[ibgdude]

Newton's forumlae worked for longer than Einstein's. How did those work out for so long?

Both Newton's equations and Einstein's were extremely close approximations to the truth/underlying reality, and so they only were/will be disproven when measurement capabilities catch up to the theory. In addition, Einstein's equations may yet last far longer than Newton's, we don't yet know.

[Minerva]

If they mean to say that Sir Alber Einstein is wrong then how did his formulas and theorems work out well this long?

Who said this? The CNGS/OPERA physicists certainly didn't say this.

There are only two kinds of people who say things like this - pseudo-physicist crackpots and annoying journalists. Both groups have been saying that for years, though, it's not really novel.

[Shivahn]

Newton's forumlae worked for longer than Einstein's. How did those work out for so long?

Both Newton's equations and Einstein's were extremely close approximations to the truth/underlying reality, and so they only were/will be disproven when measurement capabilities catch up to the theory. In addition, Einstein's equations may yet last far longer than Newton's, we don't yet know.

Oh, I know, I'm just bad at getting my point across. That post was meant to be rhetorical, since hopefully anyone who considers it will come to the conclusion that slightly incorrect (or special-case) equations can persist as what people believe to be universal for quite some time.

[dockaon]

This article:

Less technical article:
http://www.nature.com/news/2011/111005/full/news.2011.575.html

seems to be saying that a change in the cross section of the neutrinos, a change in their probability of detection, I guess, might give the appearance of a shift in time forwards. However, I can't quite figure out what the paper means by this. Can anyone explain it more simply? Quote from the article: "The apparent shift in TOF is thus of the order of the relative variation of the cross section times the rising time of the bunch. Note that an apparent advance of the rising edge can be obtained with negative values of [epsilon], that is average cross section decreasing with time."

Basically, if the detection cross-section is varying, it distorts the shape of the time of arrival curve. If you don't account for this, when you fit the curve it could shift what you measure as the time of the rising or falling edges of the curve. The size of the effect depends on the change in cross-section and the length of the rising and falling edges. Since the length of the rising and falling edge is ~500 ns, it would only need to be a 10% change in cross-section. Additionally, the distortion doesn't significantly change the shape of the rising and falling edges, so it wouldn't necessarily be noticeable.

The change in cross-section could be because the neutrino detection cross section is dependent on the energy of the neutrinos and they are grouping all the neutrino's they're detecting into the same measurement when the energy varies over a considerable range. So, if for some reason the energy of neutrinos varies during the burst in the right way you could get this result. I don't know how likely that is, but they can check for it by changing the burst shape. Presumably the Fermilab experiment would also have a different burst shape with a different energy distribution so it would give a different velocity.

[TrlstanC]

This article:

Less technical article:
http://www.nature.com/news/2011/111005/ ... 1.575.html

seems to be saying that a change in the cross section of the neutrinos, a change in their probability of detection... Quote from the article: "The apparent shift in TOF is thus of the order of the relative variation of the cross section times the rising time of the bunch. Note that an apparent advance of the rising edge can be obtained with negative values of [epsilon] , that is average cross section decreasing with time."

Basically, if the detection cross-section is varying, it distorts the shape of the time of arrival curve. If you don't account for this, when you fit the curve it could shift what you measure as the time of the rising or falling edges of the curve. The size of the effect depends on the change in cross-section and the length of the rising and falling edges. Since the length of the rising and falling edge is ~500 ns, it would only need to be a 10% change in cross-section. Additionally, the distortion doesn't significantly change the shape of the rising and falling edges, so it wouldn't necessarily be noticeable.

Is that the right link above? It takes me to an article referencing the force of gravity affecting the two clocks differently, and doesn't mention anything about detection. I was wondering before if string theory made any predictions about the maximum length of a neutrino (or more specifically the area where we have chances of detecting a neutrino) or if the orientation would affect the chances of detection, but the best answer was:

It's ruled out by the things we already know. String theory does not change the quantum mechanics and QED we know, it changes things at lower scales.

So, I'm assuming that the ~500 ns is an empirical measurement and not a theoretical prediction? At the speed of light a difference of 500 ns would mean about 150m, right? I believe the error (assuming it is an error) in the OPERA measurements was around 18m, or about an order of magnitude smaller - which would seem to imply that it's small enough to be accounted for by small mistakes in the calculation or measurement of the size/shape of the arrival curve. But it would be interesting to see the original paper that reviews that possibility.

[ibgdude]

Sorry for the confusion, I was thinking of:
http://arxiv.org/PS_cache/arxiv/pdf/1110/1110.0239v1.pdf
I edited my original post. Thanks for the explanation.

[TrlstanC]

Ahh, I didn't realize that this experiment was using two different kinds of detectors, one kind at CERN (a Beam Current Transformer, something like this) and a different kind at LNGS in Italy, using bricks of photographic emulsion films (picture here). I was assuming that at least one of the two, and possibily both were like the water/phototube detector used at the Super-Kamiokande Detector in Japan or SNO. But I guess that the size of these "older" detectors wouldn't allow for the necessary measurement accuracy, at least in terms of timing? I'd think that they would be at least as good at detecting individual neutrino interactions, if not better?

[teacupthesauceror]

I would like to wave the "imaginary numbers are really real!" banner before I do anything else. Because they are. Negative numbers aren't measurable until you define an origin.

Now, crazy theory time: the neutrinos, having complex rest mass, were moving in complex time. We only measured the real component of their travel time, and so it looked like they were travelling too fast. This might actually be the wormhole theory stated in a weird way.

Or, they got teleported to the Lost island to help move Jack & co around, and then arrived back a mite too soon because smoke monsters can't use calculators.

To be honest, both of these theories are probably equally likely, but I am curious as to how complex-massed particles would behave, and how we go about measuring complex quantities.

EDIT: Oh, also my A-level physics taught me that the speed of light is not the limit for the rate of expansion of space. Is this entirely untrue, or could it have some sort of effect if it is?

[eSOANEM]

complex rest mass

I am unsure how to interpret this physically. Particles with real rest mass have to move below c, those with imaginary mass above c; as such, I cannot see a way to say what speed the particle must move at.

For another thing, for standard tachyons, E²=E₀²+p²c² still provides real values of E (E₀ is negative, but, because the lorentz factor is negative and imaginary p²c² is positive) IIRC this is an important part of the argument for tachyons having imaginary mass. Furthermore, if we let E₀ be complex, then it will generally have a different imaginary part to p²c² and so the energy will be a complex number which again is hard to interpret.

What I am almost certain you will not get, is a meaningful answer as to which direction in time it moves.